1. Field of the Invention
The present invention relates to a suction catheter used in a treatment where the suction catheter is inserted into a blood vessel to suck out and remove an object such as a blood clot therefrom. Specifically, the present invention relates to a technique that is used when objects cause an occluded blood-vascular system, such as in the case of cerebral infarction or myocardial infarction, for the purpose of retrieving and removing the objects, easily and smoothly, from the blood vessel without allowing the objects to flow down the stream.
2. Description of the Related Art
A number of diseases are known to be caused by an occluded blood vessel. For example, each of the cerebral infarction and the myocardial infarction is a disease caused by an occluded arterial system of the corresponding organ. An economy-class syndrome is a potentially fatal disease that is caused by an occluded pulmonary blood vessel due to a blood clot formed in a leg vein.
The blood clot formed in a blood vessel is conventionally removed by use of an apparatus inserted into the blood vessel mainly in accordance with any one of the following two known methods. In one method, an object, such as a blood clot, is removed by being sucked out with the opening at the leading end of the suction catheter being brought into direct contact with the object. In the other method, the blood clot is firstly fractured, and the fractured fragments of the blood clot are then sucked out by the suction catheter.
For example, the following techniques have been proposed. A suction catheter employed in a proposed technique includes: a catheter main body to be inserted into the blood vessel; and a vibrator that makes the catheter main body vibrate. The vibrating catheter main body is brought into contact with a blood clot, and thus the blood clot is gradually fractured from the surface. According to this technique, the blood clot can be quickly removed without damaging the blood vessel. For more detail, see Japanese Patent Application Publication No. 2005-95410 (Patent Document 1).
A suction catheter employed in another proposed technique includes an actuator provided near the leading end of the catheter. When the actuator is made to vibrate, the vibration in turn makes the leading end of the catheter vibrate. The leading end of the vibrating catheter or an irregular face formed at the leading end is used for chipping away the adjacent objects. For more detail, see Japanese Patent Application Publication No. Hei 9-192230 (Patent Document 2).
FIG. 13 shows a suction catheter 100 employed in still another proposed technique. The suction catheter 100 includes an obliquely-formed leading-end portion 101a. The leading-end portion 101a is brought into contact with the object, such as a blood clot, while the inside of a lumen 111 of a catheter main body 101 is being vacuumed. Thus, the object is removed by the sucking force. An example of the suction catheter of this type is a blood-clot suction catheter that is commercially available under the registered trade name Thrombuster from Kaneka Medix Corp. Another example of the type of suction catheter is a catheter for removing embolus in the central circulatory system that is commercially available under the registered trade name Eliminate from Clinical Supply Co., Ltd.
A suction catheter employed in still another proposed technique includes a taper-shaped spiral portion provided at a leading-end portion of the suction catheter main body. The spiral portion has a coil-shaped piece wound up by at least one turn. A catheter for fracturing objects is disposed inside the spiral portion, and ejects a jet stream of a liquid to fracture an object (for example, a blood clot) in the blood vessel. The object thus fractured is then sucked up from the leading-end portion of the catheter, and is taken to the outside. For more detail, see Japanese Patent Application Publication No. Hei 2006-271693 (Patent Document 3).
A suction catheter employed in still another proposed technique includes a tubular body that has an opening for ejection and an opening for suction. To dissolve an object to be dissolved, a dissolving agent is ejected out from the opening for ejection to the object to be dissolved. Parts of the object to be dissolved may remain un-dissolved. Such fine fragments of the object to be dissolved are sucked into the tubular body from the opening for suction. In addition, mechanical means for generating vibrations is provided to the tubular body so as to fracture the object to be dissolved. With the suction catheter described above, fine fragments of a blood clot that has been fractured and left undissolved are sucked into the tubular body from the opening for suction. For more detail, see Japanese Patent Application Publication No. 2006-263125 (Patent Document 4).
A suction catheter employed in still another proposed technique is provided with a vibrator. An irregular-surface portion is formed in the outer circumferential surface of the leading-end portion of the suction catheter. The vibrator makes the irregular-surface portion vibrate, and the vibrating irregular-surface portion chips away the atheroma formed in the arteriosclerotic narrowed lesion. The chipped fragments of the atheroma is sucked from the opening portion for suction at the leading-end portion of the catheter, and taken out of the body. For more detail, see Japanese Patent Application Publication No. 2000-279525 (Patent Document 5).
Neither the means disclosed in Patent Document 1 nor the means disclosed in Patent Document 2 has an enough ability to easily and smoothly remove a blood clot. Likewise, the product with an obliquely-formed leading-end portion does not have an enough ability to easily and smoothly remove a blood clot.
In all of the means disclosed in Patent Documents 3 to 5, the position where the blood clot is subjected to fracturing or the like is away from the position where the blood clot is to be retrieved. For this reason, when the direction of blood flow is not favorable, the fragments of the blood clot may possibly flow away down the stream. For example, when a blood clot is removed from a blood vessel located in the head, the catheter has to be inserted from the upstream side of the blood clot in the direction of blood flow. Accordingly, the fragments of the blood clot readily flow away down the stream unless the fragments of the blood clot are retrieved substantially at the same time of the fracturing or the like. When the original blood clot is formed in an arterial system, the fragments of the blood clot that have flowed down the stream may cause a new blood clot to be formed in a peripheral capillary.
The description given thus far reveals some of the requirements for a suction catheter used for sucking and removing an object, such as a blood clot, formed inside a blood vessel. What follows are some examples of such requirements.
1) To have an enough ability to remove the blood clot.
2) To be capable of preventing the blood-clot fragments from flowing down the stream.
3) To allow the cutting and the suction of the blood clot to be carried out safely.
4) To follow the complex bending of the blood vessel.
None of the suction catheters that have been proposed thus far satisfies all the above-mentioned requirements. Accordingly, what has been longed for is a proposal for a suction catheter that is capable of retrieving and removing, easily and smoothly, an object, such as a blood clot, formed inside a blood vessel from the blood vessel without allowing the flowing-away of the object down the stream.